Near field communication or coupling is a technology used for System in Package (SiP) and three-dimensional chip integration. Three-dimensional integrated circuits (3D ICs) refer to integrated circuits manufactured by stacking silicon wafers and interconnecting them for greater density and power scaling. 3D ICs are currently used in various applications including 3D memory interfaces such as High Bandwidth Memory. Two-and-a-half-dimension (2.5D) integrated circuit is another example of SiP.
3D ICs may be mechanically interconnected using various techniques known in the art such as wire bonding, flip chip and through silicon vias (TSV). However, these techniques may be costly or suffer from reliability issues. In addition, these techniques may not be suitable for applications requiring high bandwidth.
Alternatively, two-dimensional (2D), 2.5D or 3D ICs may be interconnected using Near-Field Wireless Connection or Near Field Wireless Coupling (NFC) without mechanical interconnection. The chips may be coupled wirelessly via inductive couplers, capacitive couplers or transmission line couplers. In NFC, one or more inductors are placed on one or more chips. Magnetic flux is generated by a transmitting inductor. A receiving inductor on another chip converts the magnetic flux to electrical current. In inductive coupling, the chips may be stacked so that the inductors overlap from one chip to the other. Inductive coupling may also occur at the chip edge when chips are brought in close proximity as reducing distance between the inductors improves transmission efficiency. Such edge-to-edge coupling may be found in 2D or 2.5D ICs where two chips are placed side-by-side. Further, when the distance between inductors increases, the size of the inductors commensurately must be increased to compensate for the reduced coupling strength. Compared to mechanical connections, NFC may provide a cost, performance and reliability advantage. NFC techniques are less costly and may provide improved performance compared to other SiP IC integration methods, but conventional NFC techniques tend to suffer from reduced coupling efficiency.
Further, conventional inductors used for various applications including NFC and for bandwidth extension require large areas on a substrate or chip.
Additional difficulties with existing systems may be appreciated in view of the Detailed Description of Example Embodiments, below.